Several methods and devices for detecting leaks in pipes are known from the prior art.
A method and device for detecting and locating leaks in buried pipelines is disclosed in U.S. Pat. No. 3,817,086 to Dorgebray. That reference discloses a method and device for detecting and locating leaks in buried pipes under pressure that includes a detection scraper piston that is moved with a flow of liquid being transported in the pipeline. The detection scraper piston is driven by the liquid flow in the pipe and utilizes a differential pressure measuring device that includes pressure-sensing elements that can be constituted by strain gauges carried by deformable diaphragms or other pressure transducers having low inertia. The method of leak detection consists in continuously measuring the displacement of the piston from a predetermined zero point as well as the difference between the pressure within the compartment and an intermediate pressure between those prevailing on the upstream and downstream sides of the piston.
There are other methods for detecting leaks in oil pipelines. Some of these methods entail the use of radioactive tracers and consist of passing through the pipeline a volume of fluid in which a radioactive tracer has been dispersed, usually by dissolution, then removing practically the entire tracer content from the pipe by rinsing and, if necessary, by passing the scraper piston within the interior, and finally, in moving a detector piston through the line in order to detect the points at which the tracer has been absorbed in the soil surrounding the pipeline after escaping from the pipeline through leaks during passage of the radioactive fluid. For example, a method of this type is described in French Pat. No. 2,088,609.
Further, attempts have been made to provide an apparatus for detecting and locating leaks in pipelines that includes a detection probe constructed of a tube open at both ends and having an aperture in the wall thereof. An airflow measuring device is utilized to monitor airflow through the aperture. A separate, annular sealing ring is disposed adjacent each end of the tube for defining a sealed annular volume within the pipe adjacent the tube, the annular volume being bounded by the pipe, the tube and the sealing rings. When the detection probe is adjacent a leak in the pipe, a flow of air through the aperture and into the annular volume occurs and is detected by the airflow measuring device indicating the presence of a leak. However, in order to use this apparatus, it is necessary to pressurize the pipe to a pressure in excess of the pressure at the exterior of the pipe adjacent the leak so that air flows from the interior of the pipe to the exterior of the pipe.
Therefore, a need exists for a method and device for detecting and locating leaks in pipelines that cannot be filled with a fluid, or where it is desired to test a pipe without pressurizing the entire length of pipe to be tested.